OpenEuphoria

2. Re: exit command

• Posted by jeremy (admin) Apr 07, 2009
• 937 views

It's there. The manual is going to undergo some changes to make it easier to find things, it is a bit difficult to locate them right now. What you want is:

http://openeuphoria.org/docs/eu400_0009.html#_59_LanguageReference

Specifically:

http://openeuphoria.org/docs/eu400_0015.html#_121_exitstatement

Jeremy

4. Re: exit command

• Posted by jeremy (admin) Apr 07, 2009
• 1024 views

The BASIC for is very limited. Two words were adopted because break from a if/switch doesn't happen that often and we didn't want to require having a label, which if we used just one word we would have to label just about everything. Here is an example:

for i = 1 to 10 do 
    for j = 10 to 1 by -1 do 
        if j > 5 then  
            exit for 
        end if 
    end for 
end for 

What would happen?

Now, say we use the same word for everything:

for i = 1 to 10 do 
    for j = 10 to 1 by -1 do 
        switch j do 
            case 1 do 
                exit 
        end switch 
    end for 
end for 

Now, in the above situation, since we use two keywords, it's clear that exit will exit from the loop. exit leaves loops, break leaves decision constructs. Now, we use labels instead of the BASIC [for|while|if|loop] construct for this reason:

for i = 1 to 10 label "top" do 
    for j = 1 to 10 label "middle" do 
        for k = 1 to 10 do 
            if k = 5 then exit end if -- exits for k = 1 to 10 
            if k = 3 then exit "middle" end if -- exits for j = 1 to 10 
            if k = 2 then exit "top" end if -- exits for i = 1 to 10 
        end for 
    end for 
end for 

If you only have the ability to exit one loop at a time, you must introduce a state variable which is a mess:

integer break_i=0, break_j=0 
 
for i = 1 to 10 label "top" do 
    for j = 1 to 10 label "middle" do 
        for k = 1 to 10 do 
            if k = 5 then  
                exit for -- exits for k = 1 to 10 
            end if              
            if k = 3 then  
                break_j = 1 
                exit for -- exits for k = 1 to 10 
            end if  
            if k = 2 then  
                break_j = 1 
                break_i = 1 
                exit for -- exits for k = 1 to 10 
            end if  
        end for 
 
        if break_j then 
            break_j = 0 -- reset flag 
            exit for 
        end if 
    end for 
 
    if break_i then 
        break_i = 0 -- reset flag for clarity 
        exit for 
    end if 
end for 

Jeremy